The present invention is used to improve air assists for insuring uniform conveying of particulate or powdered material in a dense phase bulk material handling system, with minimization of the amount of energy used for maintaining adequate transporting of the powered or particulate material.
Dense phase transporter systems with regulated pressure air assists are illustrated in U.S. Pat. No. 5,240,355 owned by the assignee of this application. U.S. Pat. No. 5,240,355 discloses a dense phase conveying system with a conveying conduit or line that carries material under fluid pressure from a transport vessel to a receiver bin. At selected intervals along the conduit, nozzles are provided for introducing a flow of air under regulated pressure in transport zones to assist moving the material in each of the zones. The pressure in the assist nozzles is reduced in zones approaching the receiving bin, in order to minimize the wasted air.
In U.S. Pat. No. 5,224,802, a method of controlling the infeed of air from an auxiliary conduit of a pneumatic conveyer installation into a tubular conveyer conduit is illustrated. However, the valve arrangement used with that device, while using a type of pressure sensing at locations upstream and downstream of the air assist shown, has the possibility of a backfeed of air and particles from the conveying conduit into the valve arrangement, which can cause malfunctions of the valve and unreliable operation.
Various other methods for unblocking conveying conduits of slugs of particular material have been tried, utilizing similar air assists. For example, U.S. Pat. No. 4,909,676 illustrates another apparatus for conveying materials, which introduces additional gas at selected portions of the conveyer line when slugs or blockages occur.
U.S. Pat. No. 4,955,761 also describes a control device similar to that shown in U.S. Pat. No. 5,224,802, except that a spring return is used for a slider valve that controls the air flow. The same type of problems occur in this device, in that conduit connections to the valve can result in backfeeding materials into the control valves used.
Another drawback of the prior art devices is that they do not efficiently utilize energy for conveying.